Water, Water Everywhere! Biology

Objectives To understand the concept of surface tension and the effect of a surfactant To understand cohesion and adhesion of water To see the hydrophobic, polar and non- polar properties of water

Procedure Water in a Penny Effects of Detergent Glass and Parchment paper Water and Oil Water, Oil and Coloring

Results/ Data Water on a Penny How many drops from your medicine dropper are in each cm 3 (mL)? How much water is in each drop? Predictions: Table of each person’s prediction of how many drops of water before overflowing on the penny. Include actual data when experiment is complete. Draw picture of penny with 1 drop of water, half full, and almost overflowing.

Results/ Data Detergent/Surfactant Effects Same type of data as “water on penny”

Results/Data Glass and Parchment Paper Prediction (drawing) of shape of water drop on glass slide and parchment paper Drawing of water drop on glass slide and on paper (actual).

Results/ Data Water and Oil Predict what will happen if you add cooking oil to water. Oil will float on top of the water Oil will sink to the bottom of water Oil will dissolve in the water Oil will become mixed up with the water Something else?

Results/ Data Record observations of water and oil in test tube Water, Oil and Coloring Predict what will happen when a few drops of coloring are added to the oil/water mixture.

Conclusions Water on a penny: 1. Explain the behavior of the water in the penny in terms of cohesion. 2. Did the detergent make a difference on the # of drops that filled the penny before overflow? Describe/Explain. Relate to cleaning agents.

Conclusions Glass and Parchment Paper Explain the differences in drop behavior in terms of adhesion and formation or absence of hydrogen bonding.

Conclusions Water and Oil Which is less dense? What cause water molecules and oil molecules to separate from one another? (Think polar, non-polar, hydrogen bonding)

Summary